Patent Literature 1 discloses a technique for continuously or intermittently applying an electron beam to a processing object along the width direction of the processing object. The electron beam is applied by positioning the focus of the electron beam so that the focus is remoter than the surface of the processing object when the electron beam is perpendicularly incident on the front of the processing object. The intensity of the electron beam at the center in the width direction of the processing object is thereby reduced, while the intensity of the electron beam at the opposite ends in the width direction of the processing object is thereby increased. As a result, the electron beam is applied uniformly along the width direction of the processing object.